CMM4 No Sync ??

Products PMP
1

any ideas on trouble shooting this issue? Brand CMM4 worked fine for 3 Weeks all of the sudden no sync. We moved the cone higher and has a completly unobstructed view of the southern skies. It says my antenna connection is good. It sees 8 Satellites but will not track any of them. Any help would be greatly appreciated.

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2

Did your issue get resolved? If not, did you open a support ticket?

I have never seen this issue occur, and likely we'd need more information to help you solve it...

3

urgent help please we have this exact same issue, cmm4 been up for a couple of years and within the last couple of months we have had this error twice, we have it at the moment and don´t know what to do

4

The first thing I would do is get a known good antenna, measure the resistance across it, and then measure the resistance in the antenna at the site where you're having the problem.  If condensation gets inside the antenna, it will lower the resistance and cause problems.  The CMM will tell you if it the resistance gets too low, but there's some area for problems before that happens.

If that is the problem, I stopped condensation as a particularly difficult site by sealing the seam at the base of the cone with butyl, then putting a flat sheet of butyl across the bottom between the mount and antenna and putting the mounting screws through it.  I then butyl and electrical taped the connector.  It's a perfect seal, so you can dunk it in a lake without anything getting in.

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5

installed a  brand new spare one from cambium and it does the same thing, thanks the for the imput though.  Its only happening when we have rain or heavy cloud must be cmm4 is not as powerful as it used to be

6

Did you replace the GPS cable as well?

7

We have not changed the design in any way, so it's unlikely that it's "not as powerful as it used to be", but there could be some kind of interference in that area, causing sensitivity issues.

As you might note, we never got any further with the prior customer either.  Have you opened a support ticket to try to troubleshoot this further?

8

I'm sorry I have not updated this original posting, but the only thing that would fix it would be a hard power reset to the CMM4 the software reboot still would not fix the issue and it has happened one other time since.  I have a hard time saying it is a cabling issue when it tells me anntenna connection is OK and not under current. It also says that Satellites are visable its just not communicating with them. This is the rack mountable CMM4 ifthat helps any. Thanks

9

yep we replace the cable also with brand new one

10

there is no interference in the area

11

I agree Ryan, satellites are visable but cannot connect to them !!!

13

In discussion with engineering, a few things came up: 

1) Does the problem come and go, or is it always constant at that location?

2) Have you tried relocating the GPS antenna to another location, it seems that something may be interfering with the satellite signals at the current location.

Engineering seems to really be leaning toward interference in the area... this interference is likely between 800-1600 MHz (outside the radio band), which causes issues with the GPS signals (which are typically at 1575 MHz).  The CMM can see the satellites but cannot establish communications.

14

Further engineering input...

Is this occurring in the US, or another country?  

There has been cases of this occurring where the offending equipment is GSM transmitters, (operating from 775-795 MHz).  The second harmonic of this transmission could directly interfere with the GPS signal.

We would still recommend to move the GPS antenna lower on the tower or away from the mean beam of the GPS antennas or their base station racks, or just move it in 10 foot increments up, down, and sideways.  The tower engineer might help by providing all of the freq. transmitted at the site and where their antennas are located.  It is amazing that the GSM base station racks can radiate a strong 2nd harmonic, but we have had this occur with our equipment before, and have resolved it by moving the antenna.

15

So if you don't mind me asking, What was the fix for this? I have a CMM4 with 11 visable satellites but tracking none and antenna connection OK going on right now myself.

Thanks. 

16

Hi Brandon, we did not find a solution, we ended up purchasing a new CMM4 and switch........